Make DataUseTabModel and DataUseMatcher more independent

chrome/browser/android/data_usage/external_data_use_observer.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/data_usage/external_data_use_observer.h"
 
 #include <utility>
 
+#include "base/bind.h"
+#include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/task_runner_util.h"
 #include "chrome/browser/android/data_usage/external_data_use_observer_bridge.h"
 #include "components/data_usage/core/data_use.h"
@@ skipping 107 matching lines @@
 
 // static
 const size_t ExternalDataUseObserver::kMaxBufferSize = 100;
 
 ExternalDataUseObserver::ExternalDataUseObserver(
     data_usage::DataUseAggregator* data_use_aggregator,
     const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner)
     : data_use_aggregator_(data_use_aggregator),
       external_data_use_observer_bridge_(new ExternalDataUseObserverBridge()),
-      data_use_tab_model_(new DataUseTabModel()),
+      data_use_tab_model_(new DataUseTabModel(
+          base::Bind(&ExternalDataUseObserverBridge::FetchMatchingRules,
+                     base::Unretained(external_data_use_observer_bridge_)),

[tbansal1, 2016/07/18 17:04:38]

Add comment about why it is okay to use base::Unretained here. Essentially show
that the bridge is guaranteed to be non-null anytime this callback is run.

Same below.

[Raj, 2016/07/19 00:19:02]

Done.

+          base::Bind(
+              &ExternalDataUseObserverBridge::ShouldRegisterAsDataUseObserver,
+              base::Unretained(external_data_use_observer_bridge_)))),
       last_data_report_submitted_ticks_(base::TimeTicks()),
       pending_report_bytes_(0),
       ui_task_runner_(ui_task_runner),
       previous_report_time_(base::Time::Now()),
       last_matching_rules_fetch_time_(base::TimeTicks::Now()),
       total_bytes_buffered_(0),
       fetch_matching_rules_duration_(
           base::TimeDelta::FromSeconds(GetFetchMatchingRulesDurationSeconds())),
       data_use_report_min_bytes_(GetMinBytes()),
       data_report_submit_timeout_(
           base::TimeDelta::FromMilliseconds(GetDataReportSubmitTimeoutMsec())),
 #if defined(OS_ANDROID)
       app_state_listener_(new base::android::ApplicationStatusListener(
           base::Bind(&ExternalDataUseObserver::OnApplicationStateChange,
                      base::Unretained(this)))),
 #endif
       registered_as_data_use_observer_(false),
       weak_factory_(this) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   DCHECK(data_use_aggregator_);
   DCHECK(io_task_runner);
   DCHECK(ui_task_runner_);
   DCHECK(last_data_report_submitted_ticks_.is_null());
 
   ui_task_runner_->PostTask(FROM_HERE,
                             base::Bind(&DataUseTabModel::InitOnUIThread,

[tbansal1, 2016/07/18 17:04:38]

Is it possible that this initialization calls the bridge callback when bridge is
not initialized?

[Raj, 2016/07/19 00:19:02]

Removed this. InitOnUIThread() is not needed.

-                                       base::Unretained(data_use_tab_model_),
-                                       external_data_use_observer_bridge_));
+                                       base::Unretained(data_use_tab_model_)));
 
   // Initialize the ExternalDataUseObserverBridge object. It is okay to use
   // base::Unretained here since |external_data_use_observer_bridge_| is owned
   // by |this|, and is destroyed on UI thread when |this| is destroyed.
   ui_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&ExternalDataUseObserverBridge::Init,
                  base::Unretained(external_data_use_observer_bridge_),
                  io_task_runner, GetWeakPtr(), data_use_tab_model_));
 }
@@ skipping 277 matching lines @@
   hash = hash * 23 + hash_function(k.label);
   hash = hash * 31 + hash_function(k.tag);
   hash = hash * 43 + k.connection_type;
   hash = hash * 83 + hash_function(k.mcc_mnc);
   return hash;
 }
 
 }  // namespace android
 
 }  // namespace chrome